The present disclosure relates generally to an imaging system and, more particularly, to an imaging system implemented using multichip packaging.
Millimeter wave (MMW) imaging systems, hereinafter referred to as imaging systems, are used for many applications, such as aviation, including airport and aircraft safety and all-weather vision, medical and plasma diagnostics, non-destructive testing for voids and delaminations in composite materials, remote sensing of agricultural and environmental conditions, and a wide variety of defense, security, and law enforcement purposes. An imaging system generates an image of an object that is viewed by the imaging system using an array of pixels, each including a respective antenna, that are used in conjunction with sensor optics and various image processing electronics to produce the image. Such imaging systems need to be able to be installed under a wide variety of conditions and in a wide variety of locations, depending on the particular application for which the imaging system is used; size and/or portability issues regarding an imaging system may come into play in some applications.
Each antenna in the imaging system is associated with a respective receiver circuit, with one or more receiver circuits being contained in a semiconductor receiver die. Conventional die level packaging assembly may be used as the packaging technology for the various components that make up an imaging system. In die level assembly packaging, the receiver dies are adhesively or eutectically mounted to a substrate, and electrical interconnections, both between receiver dies and from receiver die to substrate, are formed by wire bonding. Such die level assembly packaging has various limitations when implemented for higher pixel count arrays, as the number of receiver die required grows rapidly. Therefore, even a relatively small 64×64 pixel array requires placing up to 4,096 discrete receiver dies and upwards of 16,384 wire bonds to interconnect the array. The wire bonds require a relatively large amount of space as compared to the receiver dies, increasing the array size. For example, since about 1.5 millimeters (mm) of space must be allowed between the dies for wire bond access, in the case of the 64×64 pixel array, the wire bonds may increase the array size by about 96 mm, which may represent about 75% of the area of the array. This in turn increases the size of the sensor optics needed for use with the array, resulting in a relatively large overall imaging system. Further, each wire bond is a potential failure point, which may affect the reliability of the array in the imaging system. Mounting the individual antennae to their respective receiver dies may also be a relatively complex process.